1. Field of the Invention
This invention relates to a particle analyzing apparatus, and in particular to a so-called flow cytometer for applying laser light to a cell-suspended solution flowing at a high speed, detecting the scattered light or fluorescent light by the cellular particle and analyzing the property and structure of the cellular particle.
2. Description of the Prior Art
As shown in FIGS. 1 and 2 of the accompanying drawings, in a flow cytometer, a cell-suspended solution is made to flow to a flow section 2 of minute rectangular cross-section (e.g. 70 .mu.m.times.20 .mu.m) in a flow cell 1 with the sheath liquid around said solution, and is hydrodynamically converged at a predetermined location 3, and an irradiation light 4 entering thereinto is also optically converged at said location.
A light receiving system 5 to 8 for forward scattered light and side scattered light or fluorescent light is fixedly provided on the assumption that said converging location does not fluctuate with time. Reference numerals 5 and 6 designate lenses, and reference numerals 7 and 8 denote photodetectors. However, the hydrodynamic converging location has a high possibility of fluctuating with time and, when the hydrodynamic converging location, i.e., the position of a particle to be examined, is displaced in a direction orthogonal to the direction of incidence of the laser, i.e., the vertical direction in FIG. 2, there occur the following problems. The intensity of the laser light strictly has a Gaussian distribution in a direction orthogonal to the direction of incidence of the laser as shown in FIG. 3 of the accompanying drawings and therefore, when the hydrodynamic converging location is displaced as indicated by a-c in the direction orthogonal to the direction of incidence of the laser, the light reception output of the side scattered light or the fluorescent light and further the light reception output of the forward scattered light are varied. If an attempt is made to flatten the intensity distribution of the irradiation light applied to the particle to be examined in order to eliminate this problem, the density of condensing energy will be reduced and an increase in the power of the light source will become necessary.
On the other hand, the center axis of the laser beam may sometimes be displaced relative to the particle to be examined in a direction perpendicular to the direction of application and again in such case, said light reception outputs are varied and therefore, accurate analysis of the particle cannot be accomplished.
Further, displacement of the particle to be examined causes the condensation distance of the light receiving optical system to be varied and thus, the variations in the light reception outputs based thereon must be taken into consideration. Furthermore, any variation in the intensity of the laser light illuminating the particle to be examined must be taken into consideration.